1. Field of the Invention
This invention relates to methods of recalibrating laser measurement systems and particularly to methods of recalibrating laser measurement systems in situ.
2. Description of the Prior Art
Laser measurement systems or other light-based systems, which employ triangulation or polar coordinates to determine the position of retro-reflective targets position at specific known reference points, such as on the frame of a vehicle, have been used for years. Examples of such a system can be found in U.S. Pat. No. 5,801,832 and its related patents and published applications. In such a system, a beam of the laser scanner is split into two beams by a 50/50 beam splitter, each beam then directed to a rotating mirror. The rotating mirrors direct the laser beams in a 360-degree arc or circle, with both beams being directed in a single plane. The distance between the two laser beams forms the base of the triangle and the two angles generated by the rotating mirrors provide the position of the target. The system requires each of the rotating mirrors to be “synched” to the mechanical centerline of the laser of the laser scanner. The synch position is typically calibrated at the factory using a table with a precision grid of targets. There are several factors in addition to synch that are taken into account during this calibration. When the unit is put into the field and measurements taken in situ, it is common for this synch reference to move which causes measurement errors.
Once errors are detected, the only present way to recalibrate the scanner is to send it back to the factory for recalibration. Such a procedure can be time consuming, costly and unproductive as the unit must be sent out meaning work using that scanner must either be put on hold or the facility must have several scanners ready for use when one more scanners is/are sent back for recalibration.